Apparatus for recording and reproducing temporally compressed digital information signal

ABSTRACT

A digital information recording-reproducing apparatus is disclosed, in which a signal temporally compressed to 1/n and transmitted is encoded for recording by a recording encoder. The rotation speed of a rotary drum is set at R 1 , and the running speed of a magnetic tape at V 1 . The signal encoded is recorded on the magnetic tape by magnetic heads. At the time of reproduction, the rotary drum is driven at a speed m/n times faster than for recording, and the magnetic tape is run at a speed 1/n times faster than for recording. The signal reproduced by the magnetic heads is decoded and restored into the original digital information signal by a reproducing decoder. As a result, there is provided a recording-reproducing apparatus having the function of time-base expansion with a reduced recording time applied to a system for transmitting and recording the software information of video or the like through radio wave or cable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a digital informationrecording-reproducing apparatus, or more in particular to a digitalinformation recording-reproducing apparatus having a time-baserestoration function.

2. Description of the Related Art

The Institute of Television Engineers of Japan Journal Vol. 47, No. 4,April 1993, pp. 494-499, describes a system conceived to transmit audioor video software through radio wave or a cable to be recorded in eachhome.

In this conventional system, however, the rate at which softwareinformation is transmitted, recorded and reproduced is fixed.Especially, no measure is taken to shorten the recording time.

Also, the problem of the above-mentioned conventional system is that thesale or rent which may be made of audio or video software requiresmanagement of information on customers, number of days rented, etc.

One such system may be interactive, in which the user requests the videosoftware he wants from the transmitting end, and the software suppliertransmits the desired software. In such a case, however, it takes apredetermined length of time before the wanted digital informationsignal is actually transmitted from the time the particular videosoftware is requested. More specifically, the transmitting end isrequired to prepare the video data to be transmitted or to stand byuntil a transmission channel becomes available. This leads to theproblem that the user cannot determine the time to start his VTR.

SUMMARY OF THE INVENTION

A first object of the invention is to obviate the above-mentionedproblems and to provide a digital information recording-reproducingapparatus having the functions of shortening the recording time andrestoring the signal on time base.

A second object of the invention is to obviate the above-mentionedproblems and to provide a digital information recording-reproducingapparatus capable of easily managing information on customers, number ofdays rented, etc.

A third object of the invention is to obviate the above-mentionedproblems and to provide a digital information recording-reproducingapparatus simple to operate, in which recording errors can be minimized.

In order to achieve the first object, according to the invention, thereis provided a digital information recording-reproducing apparatus inwhich software information is transmitted by being reduced to 1/ntemporally, the received software reduced to 1/n temporally is recordedin magnetic tape at a predetermined rate, and the recorded signal isreproduced at the rate 1/n the recording rate.

In order to achieve the second object, according to the invention, thereis provided a digital information recording-reproducing apparatus inwhich control codes such as the user number and the recording date areadditionally recorded in the recording signal so that the information oncustomers, number of days rented, etc. are managed based on the addedinformation at the time of reproduction.

According to a first method for achieving the third object of theinvention, there is provided a digital information recording-reproducingapparatus comprising a control signal generator at the transmitting endfor controlling the operating conditions of recording-reproducing means(VTR), wherein an output signal of the control signal generator istransmitted together with a digital information signal throughtransmission means before recording, and a control signal detector atthe receiving end is connected with the receiver and produces an outputsignal thereby to control the VTR in recording mode.

According to a second method for achieving the third object of theinvention, there is provided a digital information recording-reproducingapparatus comprising a control signal generator at the transmitting endfor controlling the operating conditions of the VTR, second transmissionmeans for transmitting an output signal of the control signal generator,and a control signal detector at the receiving end, wherein an outputsignal of the control signal generator is transmitted through the secondtransmission means before starting the recording, the VTR is controlledin recording mode by the output signal of the control signal detector,and the digital information signal transmitted through the firsttransmission means is recorded by the VTR.

According to a third method for achieving the third object of theinvention, there is provided a digital information recording-reproducingapparatus wherein the magnetic tape is divided into a number a ofrecording areas (a: integer of 1 or more) each assigned to one videosoftware.

The recording time can be shortened to 1/n by recording the softwareinformation temporally compressed to 1/n.

At the time of reproduction, the signal is reproduced at the rate 1/nthe recording rate, and therefore the time axis is expanded by n timesto reproduce the original software information before temporalcompression.

At the time of reproduction, the control information including the usernumber and recording date are read. In the case where the user number isdifferent, however, no reproducing operation is performed. In the caseof software rental, on the other hand, no reproducing operation isperformed after the lapse of a predetermined time from the recording. Byso doing, information on customers, the number of days rented, etc. canbe managed appropriately.

According to the first method, the control signal for controlling theVTR in recording mode is transmitted through the same transmissionchannel of radio wave or cable before the digital information signal ofthe video software to be transmitted. A demodulator at the receivingend, once it has received the control signal, immediately sets the VTRin recording mode.

According to the second method, the control signal for controlling theVTR in recording mode is transmitted through a second transmissionchannel such as the telephone line different from the transmissionchannel for transmitting the digital information signal before thedigital information signal of the video software to be transmitted. Asecond demodulator at the receiving end, once it has received thiscontrol signal, immediately or after the lapse of a predetermined time,sets the VTR in recording mode.

According to the third method, the magnetic tape is divided beforehand(preformatted) into a plurality of recording areas, each of which isassigned to a video software for sequentially recording the video datafrom the tape starting section. In the process, the recordinginformation on the video data that has been recorded in each area isrecorded in the header or tail section of the particular area, andaccording to the contents of the recording information, the next area tobe recorded is automatically selected.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a digital informationrecording-reproducing apparatus according to an embodiment of theinvention.

FIG. 2 is a block diagram showing an example configuration of arecording encoder according to the invention.

FIG. 3 is a diagram showing input and output signals of the recordingencoder shown in FIG. 2.

FIG. 4 is a diagram showing an example configuration of an ID signal.

FIG. 5 is a diagram showing a recording track pattern according to theembodiment shown in FIG. 1.

FIG. 6 is a diagram showing a reproducing track pattern according to theembodiment shown in FIG. 1.

FIG. 7 shows waveforms representing the reproducing operation accordingto the embodiment shown in FIG. 1.

FIG. 8 is a block diagram showing an example configuration of areproducing decoder according to the invention.

FIG. 9 is a block diagram showing a digital informationrecording-reproducing apparatus according to another embodiment of theinvention.

FIG. 10 is a block diagram showing an example configuration of arecording encoder according to the invention.

FIG. 11 is a diagram showing an example configuration of a controlsignal.

FIG. 12 is a diagram showing a control signal recording system accordingto another embodiment.

FIG. 13 is a diagram showing a reproducing track pattern according tostill another embodiment of the invention.

FIG. 14 shows waveforms representing the reproducing operation accordingto a further embodiment of the invention.

FIG. 15 is a block diagram showing an example configuration of areproducing decoder according to the invention.

FIG. 16 is a diagram showing an example configuration of the controlsignal according to the embodiment shown in FIG. 9.

FIG. 17 is a block diagram showing a digital informationrecording-reproducing apparatus according to still another embodiment ofthe invention.

FIG. 18 is a diagram showing an example configuration of the outputsignal of a transmitting encoder according to the invention.

FIG. 19 is a block diagram showing a digital informationrecording-reproducing apparatus according to still another embodiment ofthe invention.

FIG. 20 is a diagram showing divisions of the magnetic tape into areasaccording to another embodiment.

FIG. 21 is a diagram showing an arrangement of recording informationsignals according to a further embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described below withreference to the accompanying drawings.

A block diagram of a digital information recording-reproducing apparatusaccording to an embodiment of the invention is shown in FIG. 1. Thisapparatus roughly comprises a transmission system 100, a receivingsystem 200, and a recording-reproducing system 300. Numeral 1 designatesan input terminal, numeral 10 a transmitting encoder, numeral 20 atime-base reduction circuit, numeral 25 a modulator, numeral 30 atransmission channel, numeral 35 a demodulator, numeral 40 a recordingencoder, numeral 45 a change-over switch, numeral 50 a rotary drum,numerals 51a, 51b magnetic heads, numeral 60 a magnetic tape, numeral 70a reproducing decoder, numeral 80 a receiving decoder, and numeral 9 anoutput terminal. In the magnetic heads 51a 51b, (+) designates apositive azimuth, and (-) a negative azimuth.

In the transmission system 100 shown in FIG. 1, the digital informationsignal inputted from the input terminal 1 is encoded in a predeterminedformat by the transmitting encoder 10. The signal thus encoded isreduced temporally to 1/n by the time-base reduction circuit 20 toincrease the transmission rate by n times, followed by modulation at themodulator 25. The signal thus modulated is sent out on the transmissionchannel 30.

In the receiving system 200, the signal received through thetransmission channel 30 is demodulated at the demodulator 35. The signalthus demodulated is applied as it is to the recording encoder 40 of therecording-reproducing system 300 directly. The signal thus applied isencoded by the recording encoder 40 in a format suitable for recordingand reproduction.

A block diagram representing an example configuration of the recordingencoder 40 is shown in FIG. 2. Numeral 41 designates a memory, numeral42 an interface circuit, numeral 43 a parity generator, and numeral 44 arecording signal generator. In FIG. 2, the data demodulated at thedemodulator 35 of the receiving system 200 is stored first in the memory41 through the interface circuit 42. The demodulated data is shown in(A) of FIG. 3. The parity generator 43 generates a parity from thedemodulated data stored in the memory 41, and the parity thus generatedis stored in the memory 41. The recording signal generator 44 reads theparity and the demodulated data from the memory 41, and adding a syncsignal and an ID signal, produces a signal in block form as shown in (B)of FIG. 3. FIG. 4 shows an example configuration of the ID signalconstructed of, for example, a track number for identifying therecording track, a block number for identifying the in-track position, acontrol code such as the program number or the recording time on tapeand a parity for detecting and correcting an error of the ID signal.

The signal thus encoded for the recording system is applied to themagnetic heads 51a, 51b mounted at 180 degrees to each other on therotary drum 50 and is recorded in azimuth on the magnetic tape 60.Assume that the rotation speed of the rotary drum 50 is R₁ and thetraveling speed of the magnetic tape 60 is V₁. This recording trackpattern is shown in FIG. 5. Character P designates a track pitch, andcharacter W the width of the magnetic heads 51a, 51b. According to theembodiment under consideration, the head width W is set larger than thetrack pitch P at, say, 1.5 times as large as the track pitch P.

At the time of reproduction, the rotary drum 50 is rotated at a speed ofR₁ ×m/n, that is, m/n times (1<m ≦n) the rotational speed for recording,the magnetic tape 60 is run at a speed of V₁ /n that is 1/n times thespeed for recording, and the signal thus recorded is reproduced by themagnetic heads 51a, 51b.

FIG. 6 is a diagram showing the reproducing track pattern, in which thesolid line represents a recorded track pattern and the dashed line ascanning trace of the magnetic heads 51a, 51b. In this way, the rotarydrum 50 is rotated at a speed of R₁ ×m/n that is m/n times the rate forrecording and the magnetic tape 60 is run at a speed of V₁ /n that is1/n times the rate for recording. Therefore, the scanning pitch of themagnetic heads 51a, 51b is 1/m times the track pitch P. In spite of asmall deviation of the scanning angle, therefore, substantially a numberm of scans are effected per track. According to the present embodiment,m is assumed to be 3 for simplicity of explanation.

Waveforms representing the process for recovering signals from thenumber m of scans are shown in FIG. 7. In FIG. 7, (A) designates thetiming of driving the rotary drum at the speed of R₁ /n that is 1/ntimes the speed for recording. In this case, signals a₀, b₀, a₁, b₁, a₂,b₂, a₃, b₃ are assumed to be reproduced in that order. Character Tdesignates the rotational period. Character (B) designates the timing ofrotation at the speed of R₁ ×m/n (m=3) according to the presentembodiment, and (C) an envelope of the signal reproduced by the magneticheads 51a, 51b. In this way, three scans are effected per track. Also,as described above, the width W of the magnetic heads 51a, 51b is set to1.5 times the track pitch P. Even when the scanning angle deviates fromthe recording track angle, therefore, the on-track condition is securedfor the most part. The signal with the highest reproduction output levelis retrieved, thereby producing the original data (waveform D). Thisdata is restored to three times on time base to reproduce an intendedlow-speed signal (waveform E).

As seen from above, at the time of reproduction, the rotary drum 50 isdriven at the speed m/n times higher than for recording, and themagnetic tape 60 is made to travel at the speed 1/n times higher thanfor recording. The time-base restoration n times larger is thus madepossible.

Further, if the value m is set appropriately, a high reproductionfrequency can be obtained and the desired reproduction output level canbe secured regardless of the coefficient n of time-base restoration.Furthermore, the number m of scans per track permits data reproductioneven under the off-track condition, thus eliminating the need ofaccurate tracking control.

FIG. 8 is a block diagram showing an example configuration of areproducing decoder 70 for processing the whole reproduction systemincluding the process for retrieving the signal from the number m ofscans described above. Numeral 71 designates a memory, numeral 72 ablock detector, numeral 73 an error correction circuit, and numeral 74 areproducing signal generator. In FIG. 8, the signal reproduced by themagnetic heads 51a, 51b is first applied to the block detector 72. Theblock detector 72 detects the sync signal and the ID signal, and storesthem at a predetermined position in the memory 71 based on the tracknumber and the block number in the ID signal. The error correctioncircuit 73 corrects the error in the reproduced data using the paritystored in the memory 71, while at the same time generating a pointerrepresenting the error condition and storing it in the memory 71. In theprocess, the memory 71 is supplied with the data on the same tracknumber and the block number a number m of times. The data with the besterror state is finally stored by the pointer. The reproducing signalgenerator 74 reads the error-corrected data from the memory 71 in theorder of the track numbers and the block numbers and produces thelow-speed data restored on time base.

The low-speed data signal thus processed in the reproducing decoder 70is applied to the receiving system 200 and decoded by the receivingdecoder 80 at the transmission system. The signal thus decoded into theoriginal digital information signal is outputted from the outputterminal 9.

As described above, the receiving decoder 80 is acceptable as alow-speed processing device by being arranged in the last stage of therecording-reproducing system 300.

A block diagram representing a digital information recording-reproducingapparatus according to another embodiment of the invention is shown inFIG. 9. This embodiment is an example of a system in which the videosoftware is encrypted and transmitted as data recordable andreproducible only by the subscriber. In FIG. 9, numeral 15 designates anencryptor, numerals 52a, 52b magnetic heads, numeral 75 a decryptor,numerals 101, 102, 103 input terminals, numerals 111, 112 A/Dconverters, numerals 121, 122 bit reduction circuits, numerals 201, 202bit restoration circuits, numerals 211, 212 D/A converters, and numerals221, 222, 223 output terminals. Those component parts corresponding tothose in FIG. 1 are designated by the same reference numeralsrespectively and will not be described below. In the magnetic heads 52a,52b, (+) designates a positive azimuth, and (-) a negative azimuth.

In the transmission system 100, the video signal applied from the inputterminal 101 is A/D converted by the A/D converter 111, andbit-compressed to an appropriate rate by the bit reduction circuit 122.The audio signal applied from the input terminal 102, on the other hand,is A/D converted by the A/D converter 112 and bit-compressed to anappropriate rate by the bit reduction circuit 122. These video and audiosignals A/D-converted and bit-compressed, together with the auxiliarydata applied from the input terminal 103, are encrypted andtime-division multiplexed by the encryptor 15 and encoded by thetransmitting encoder 10. The encrypted signal, as in the embodimentshown in FIG. 1, is compressed on time base to 1/n by the time-basereduction circuit 20, modulated by the modulator 25, and sent out to thetransmission channel 30.

The receiving system 200, like in the embodiment shown in FIG. 1,demodulates the signal received through the transmission channel 30 bythe demodulator 35, and applies the demodulated data to the recordingencoder 40 of the recording-reproducing system 300.

The recording-reproducing system 300 encodes the demodulated datathrough the recording encoder 40, which data is supplied through thechange-over switch 45 to two sets of magnetic heads 51a, 51b and 52a,52b, and recorded in the magnetic tape 60 by 2-channel azimuth. The2-channel recording using the two sets of magnetic heads 51a, 51b, 52a,52b can reduce the recording frequency to one half. The rotational speedof the rotating drum 50 and the travel speed of the magnetic tape 60 areset, for example, at R₂ and V₂ respectively.

At the time of reproduction, the rotary drum 50 is rotated at the samerate R₂ as for recording (i.e., m=n). The magnetic tape 60 is run at therate of V₂ /n that is 1/n the rate for recording, and the signal thusrecorded is reproduced by a set of magnetic heads 5la, 51b. According tothis embodiment, the coefficient n for time-base reduction is setsufficiently large (the larger the value n, the better). In view of thefact that a number n/2 of tracings per track is possible even for1-channel reproduction by the magnetic heads 51a, 51b, sufficient datareproduction is possible by the same processing through the reproducingdecoder 70 as in the embodiment of FIG. 1. As a result, a single channelof reproducing circuit serves the purpose, thereby reducing the circuitsize. Also, since the rotary drum 50 is driven at the same speed as atthe time of recording, the rotation control is simplified.

The receiving system 200 receives the signal decoded by the reproducingdecoder 70, decodes through the receiving decoder 80 the signal encodedat the transmission system, decrypts through the decryptor 75 the signalencrypted at the transmission system, and thus separates the videosignal, the audio signal and auxiliary data. The video signal and theaudio signal thus separated are expanded into the original bit rate bythe bit restoration circuits 201, 202, D/A converted by the D/Aconverters 211, 212, and outputted from the output terminals 221, 222.Also, the auxiliary data thus separated are outputted from the outputterminal 223.

In this way, the video signal and the audio signal thus recorded areprotected by arranging the decryptor 75 in the last stage of therecording-reproducing system 300.

                  TABLE 1    ______________________________________    Video rate (after bit reduction)                       2.5 Mbps    Audio rate (after bit reduction)                       256 kbps (2 ch)    Auxiliary data rate                       256 kbps    Total bit rate (after encoding)                       4 Mbps    Time-base compression rate                       1/6 (n = 6)    Transmission rate after time-base                       24 Mbps    reduction    Modulation method  32 QAM    Transmission channel                       Cable (bandwidth 6 MHz)    ______________________________________

Table 1 shows a specific example of the transmission specification ofthe transmission system 100 according to the embodiment shown in FIG. 9.Assuming that the post-compression video bit rate is 2.5 Mbps, thepost-compression audio bit rate is 256 kbps, and the auxiliary data bitrate is 256 kbps, for example, the total bit rate after transmissionencoding is about 4 Mbps. With this bit rate compressed on time base to1/6 (n=6), the transmission rate is 24 Mbps. Assuming also that the CATVcable is a transmission channel, the bandwidth per TV channel is 6 MHz.If a signal of 24 Mbps in transmission rate is to be transmitted withinthe bandwidth of 6 MHz, the optimum modulation system is 32 QAM(Quadrature Amplitude Modulation).

Instead of the CATV cable used for the transmission channel in Table 1above, a communication satellite may be used for a QPSK (QuadraturePhase Shift Keying) modulation system. In such a case, the bandwidth ofthe communication satellite is about 30 MHz per channel of thetransponder, and therefore the transmission rate of about 48 Mbps isavailable. As a result, with the same bit rate as in Table 1, twosustaining program software can be transmitted simultaneously bytime-division multiplexing. Alternatively, the bit rate may be increasedtwice (with the bit rates of the reduced image and voice as 5 Mbps and512 kbps respectively and the bit rate for auxiliary data as 512 kbps)to improve the video and audio quality. Conversely, the transmissiontime may be shortened by time-base reduction to 1/12 (n=12).

                  TABLE 2    ______________________________________                   Example 1                            Example 2    ______________________________________    Input bit rate   24 Mbps    24 Mbps    Recording bit rate (after                     36 Mbps    36 Mbps    coding)    Number of recording channels                     2          2    Tape width       1/2 in.    8 mm    Tape material    Metal-oxide                                Metal-evaporated    Drum diameter    62 mm      40 mm    Drum rotation speed                     1800 rpm   1800 rpm    (recording)    Tape speed (recording)                     66.7 mm/s  28.69 mm/s    Track pitch      58 μm   20.5 μm    Drum rotation speed                     1800 rpm   1800 rpm    (reproduction)    Tape speed (reproduction)                     11.12 mm/s 4.78 mm/s    ______________________________________

Table 2 shows specific examples of the specifications of therecording-reproducing system 300 corresponding to the transmissionspecifications shown in Table 1 according to the embodiment of FIG. 9.Example 1 represents the case using an metal-oxide tape 1/2 in. wide,and Example 2 the case using a metal-evaporated tape 8 mm wide. Theinput bit rate is 24 Mbps in transmission rate as shown in Table 1, andthe recording bit rate after the encoding in the recording system isabout 36 Mbps. With two-channel recording, the recording rate is 18 Mbpsper channel. In Example 1, the drum diameter is assumed to be 62 mm, andthe recording drum rotation speed and the tape speed 1800 rpm and 66.7mm/s respectively. The related track pitch is 58 μm, and the recordingwavelength is about 0.64 μm. The use of a high-performance metal-oxidetape, therefore, can achieve a sufficient reproducing signal level. InExample 2, on the other hand, the drum diameter is assumed to be 40 mm,the recording drum rotation speed and the tape speed to be 1800 rpm and28.69 m/s, respectively. Then the track pitch is 20.5 μm. Under thiscondition, the recording wavelength is as short as about 0.42 μm, but asufficient reproducing signal level can be secured by using themetal-evaporated tape. In both Examples 1 and 2, the reproducing drumrotation speed is the same 1800 rpm as for recording, while the tapespeed is of course set to 11.12 mm/s and 4.78 mm/s respectively, whichare 1/6 the corresponding figures for recording.

A configuration of the control signal is shown in FIG. 11. The "programnumber" is information indicating the order of a program in the tape,and the "time code" indicates the lapse of time in the program and tape.The "type" is information indicating whether the digital informationsignal recorded is sold or rented. This information may be subdivided inaccordance with whether the information is sold only to a specific useror the number of days rented. The "recording date" is the date and timerecorded, and the "user No." a user registration number recorded, whichare both stored in the receiving system 200 or the recording-reproducingsystem 300.

The control code can be recorded by being distributed in a plurality ofblocks to reduce the redundancy. Also, as shown in FIG. 12, the controlcode may be recorded in a region different from the digital informationsignal. In such a case, the blocks are configured the same way as thedigital information signal recording region, and the control code isrecorded in the part where the demodulated data of FIG. 3(B) isrecorded. The control code may be written severalfold for an improvedreliability.

In the case where the user desiring the service of sale or rent ofdigital information signal proposes to the transmitting end, thetransmitting end sends to the receiving end the digital informationsignal together with the user number and the additional informationindicating the sale or rental. The receiving end discriminates the usernumber in the additional information at the recording-reproducing system300, and when they are coincident, records the information. In theprocess, the sale or rental is discriminated by the additionalinformation and recorded as type information in the control code.

According to a further embodiment of the invention, at the time ofreproduction, the rotating drum 50 is driven at the same rate R₁ as atthe time of recording, the magnetic tape 60 is fed at the rate of V₁ /nthat is 1/n times the rate for recording, and the signal thus recordedis reproduced by the magnetic heads 51a, 51b.

FIG. 13 is a diagram showing a reproducing track pattern, in which thesolid line represents a recorded track pattern and the dashed line thescanning traces of the magnetic heads 51a, 51b. In view of the fact thatthe rotating drum 50 is driven at the same rate R₁ as at the time ofrecording and the magnetic tape 60 is fed at the rate of V₁ /n that is1/n times the rate for recording, the scanning pitch of the magneticheads 51a, 51b is 1/n times the track pitch P. As a result, although thescanning angle is deviated to some degree, substantially a number n ofscans are effected per track. According to the embodiment underconsideration, n is assumed to be 3 for simplicity. Character Wdesignates the width of the magnetic heads 51a, 51b. Normally, the headwidth W is set at, say, 1.5 times larger than the track pitch P.

FIG. 14 shows waveforms representing the process of retrieving thesignal from the number n of scans. In FIG. 14, (A) designates the timingwith the rotary drum 50 driven at the conventional speed of R₁ /n. Inthis case, signals a₀, b₀, a₁, b₁, a₂, b₂, a₃, b₃ are reproduced in thatorder. Character T designates the rotational period. Character (B)designates the timing of rotation made at the rate of R₁ (n=3) accordingto this embodiment. Character (C) designates an envelope of the-signalreproduced by the magnetic heads 51a, 51b. As described above, threescans are made per track and also the width W of the magnetic heads 51a,51b is set to 1.5 times larger than the track pitch P. Even when thescanning angle deviates from the recording track angle, therefore, theon-track condition is secured for a considerable part. As a result, theoriginal data (waveform D) can be produced by retrieving the signal withthe highest reproduction output level. By expanding this signal to threetimes on time base, the intended low-speed signal (waveform E) can bereproduced.

As seen from the above explanation, the reproducing frequency can beincreased without reducing the coefficient n of the time-base reductionby driving the rotating drum 50 for reproduction at the same rate as forrecording, thereby securing the desired reproduction output level. Also,the control of the rotary drum 50 is simplified. Further, because of thenumber n of scans per track, the data can be reproduced even underoff-track conditions, thereby eliminating the need of accurate trackingcontrol.

A block diagram of an example configuration of the reproducing decoder70 for processing the whole reproducing system is shown in FIG. 15.Numeral 71 designates a memory, numeral 72 a block detector, numeral 73an error correction circuit, numeral 74 a reproducing signal generator,and numeral 302 a control signal detector. In FIG. 15, the signalreproduced by magnetic heads 51a, 51b is first applied to the blockdetector 72. In the block detector 72, a sync signal and an ID signalare detected and stored in a predetermined position on the memory 71 inaccordance with the track number and the block number in the ID signal.The error correction circuit 73 corrects an error, if any, in thereproduced data using the parity stored in the memory 71, while at thesame time generating a pointer indicating the error condition andstoring the pointer in the memory 71. In the process, although the samedata on the track number and the block number are stored a number n oftimes in the memory 71, the data in the best error condition is finallystored by the pointer. In the reproducing signal generator 74, theerror-corrected data stored in the memory 71 is read out in the order ofthe track number and the block number thereby to produce low-speed dataexpanded on time base.

The low-speed data thus decoded for the reproducing system is sent tothe receiving system 200 thereby to resolve the coding made at thetransmitting system. The signal thus decoded to the original digitalinformation signal is produced from the output terminal 9.

In this way, the receiving decoder 80 is arranged not before but afterthe recording-reproducing system 300, so that the receiving decoder 80permits low-speed processing.

The control signal detector 302 identifies the control code and decideswhether the reproduction is to be carried out. In the case of soldinformation, for example, when the user number is coincident, theinformation can be reproduced only by the apparatus that was used forrecording but not by any other apparatuses. With information on rental,by contrast, the recording data and the rental period are compared, andif the rental period has passed, the information is prevented from beingreproduced. This control operation can be alternatively performed by thereceiving system 200, in which case the control signal that has beenreproduced at the recording-reproducing system 300 is applied to thereceiving system 200.

FIG. 16 shows a configuration of the control signal according to theembodiment of FIG. 9. The encrypt information is the one required fordecryption. Normally, this information is stored in the receiving system200. This encrypt information is stored as control code, and the encryptinformation reproduced at the time of reproduction is applied to thereceiving system 200 to perform decryption. Even when the encryption ischanged, the recorded information can thus be reproduced.

Also, in the case of rented information, the encryption is regularlychanged so that no encrypt information is recorded in the control code.In this way, the information that has passed a predetermined length oftime cannot be decrypted, thereby making it possible to manage therental period.

In this configuration, it takes some time length before the user wantingto view a video software requests and receives an actual video datasignal. This is because the transmitter is required to prepare the videodata to be transmitted or to stand by until a transmission channelbecomes available. This leads to the problem of when the user can decideto start the recording-reproducing system 300. The recording-reproducingsystem 300, therefore, is desirably controlled by the video datatransmitter.

The embodiment shown in FIG. 17 represents an example of transmitting arecording-reproducing control signal multiplexed on the digitalinformation signal transmitted by satellite or cable as a transmissionchannel. For example, a signal for setting the recording-reproducingsystem 300 to a recording (REC) stand-by mode (with the drum 50 rotatedwhile the magnetic tape 60 kept stationary) is supplied from therecording-reproducing control signal input terminal 2 approximately twominutes before transmitting a video signal actually to be recorded, andthrough the modulator 25 and the transmission channel 30, is transmittedtogether with the ID code for identifying the receiving home and therecording-reproducing system 300. The demodulator 35 that has receivedthis signal sends out the received data to the recording-reproducingcontrol signal detector 65, and sets the change-over switch 45 of therecording-reproducing system 300 to the REC stand-by state.

Next, a signal for setting the recording-reproducing system 300 to RECstate is sent out about one second before transmission of the digitalinformation signal, and the recording-reproducing control signaldetector 65 sets the recording-reproducing system 300 in REC mode. Thedigital information signal is thus recorded in the magnetic tape 60.Also, at the termination of the digital information signal, a stopsignal is immediately transmitted thereby to stop therecording-reproducing system 300.

If the user confirms that the magnetic tape 60 has been inserted intothe recording-reproducing system 300 in this configuration, then theremaining operation is performed by the recording-reproducing system 300under the control of the transmission system 100. The recordingoperation can therefore be performed positively without any specialmanipulation. This control data is in one of the three modes including(1) REC stand-by, (2) REC and (3) stop, and therefore is constituted bytwo bits at most. Further, the transmitting time is not limited to theabove-mentioned value.

FIG. 18 shows a transmission data format according to an embodiment ofthe invention. In FIG. 18, a block is comprised of a sync signal, an IDdata, a parity associated with the ID data, a digital information signalto be recorded and an error correction code for the digital informationsignal. This block is commonly used and similar to the one used for PCMvoice for BS or DAT (Digital Audio Tape).

As seen from FIG. 18, the recording-reproducing control signal describedabove, together with the home and recording-reproducing (VTR) ID signal(user code), is applied to the ID data section. In the process, therecording-reproducing control signal might be recorded if the recordingformat shown in FIG. 3 is employed. It is however possible to preventonly the control signal from being recorded by the recording signalgenerator 44. Even if the control signal has been recorded, thereproducing decoder 70 can be controlled in such a manner as to ignorethe particular signal at the time of reproduction.

FIG. 19 is a block diagram showing another embodiment of the invention.In FIG. 19, the same component parts as those in FIG. 17 are designatedby the same reference numerals respectively. Numeral 26 designates amodulator, numeral 31 a transmission channel, and numeral 36 ademodulator. This embodiment is different from that of FIG. 17 in thatthe recording-reproducing control signal is transmitted through atelephone line represented by the transmission channel 31, for example,and comprises a dedicated modulator 26 and a dedicated demodulator 36.The actual transmission data, as described with reference to theembodiment shown in FIG. 17, has two-bit information. In the embodimentshown in FIG. 19, no extraneous signal is superimposed on thetransmission channel 30 for transmitting the digital information signal,and therefore the hardware of the transmitting system is simplified.Also, the modulator 26 and the demodulator 36 can be of low-speed type.

In the case where the telephone line is used as the transmission channel31 in the embodiment under consideration, however, the channelconnection time of about two seconds is required. Also, when thechannels are very much congested, the recording-reproducing system 300may not be instantaneously switched to REC mode. For this reason, theinformation predicting the recording time is preferably transmitted atthe time of transmitting a REC stand-by signal about two minutes beforethe digital information signal as mentioned above, so that therecording-reproducing system 300 may be set to REC mode just at the timeof starting the transmission of the digital information signal. Thetimer built in the recording-reproducing system 300 can of course besynchronized with the transmitting timer all the time or at the time ofsending out the REC stand-by signal. This configuration increases theamount of information controlled for the recording-reproducing system300 transmitted through the transmission channel 31. Therecording-reproducing system 300, however, can thus be positivelycontrolled to REC stand-by, REC or stop state by the transmitting end.This method can of course be applied also to the embodiment shown inFIG. 17.

The use of the telephone line as the transmission channel 31 permits thebidirectional reception according to the embodiment shown in FIG. 19.The operating conditions of the recording-reproducing system 300 canthus be decided at the transmitting end. Once a modulator and ademodulator are provided at the receiving and transmitting endsrespectively, therefore, an alarm can be issued to the user any time therecording-reproducing system 300 in malfunction. As a result, therecording operation can be performed more accurately than according tothe embodiment shown in FIG. 1.

As far as the recording-reproducing system 300 shown in FIGS. 1 and 19is controlled appropriately, the recording-reproducing system 300 propermay comprise only a change-over switch operated by the user forswitching three modes of reproduce, fast forward feed and rewind. Theapparatus can thus be operated in very simple manner.

FIG. 20 is a diagram showing an example of the recording format for themagnetic tape 60 used with the recording-reproducing system 300. In FIG.20, the magnetic tape 60 is divided into three areas along thelongitudinal direction, for example, thereby to permit continuousrecording of three types of video software.

Assuming that another set of magnetic heads 51a, 51b is added to providetwo channels with n of 6, the recording of two-hour (120-minute)software requires the consumption amount of the magnetic tape 60equivalent to 40 minutes for the conventional VTR. Generally, each moviesoftware is less than two and half hours, and therefore a 50-minuterecording area is required for each such software. If the 160-minutetape sold on the market is used, on the other hand, three pieces ofsoftware can be continuously recorded.

In the embodiment shown in FIG. 20, the magnetic tape 60 is preformattedand the intended information is recorded at the heads of the threerecording areas 1, 2 and 3 into which the magnetic tape 60 is divided.These information include the area number, the recording time, therecording date, and if required, the title. Further, the heads of theareas 2 and 3 have recorded therein the recording time and date of thedigital information signal respectively for the preceding arearespectively.

Explanation will be made about the case in which three types of softwareare recorded at different dates and times. Normally, the digitalinformation signal is recorded in the areas 1, 2 and 3 in that order.Upon completion of recording up to the area 3, the magnetic tape 60 isrewound and then the area 1 is recorded. At the same time, the recordingdate in the head and tail portions of the area 1 is read. In the casewhere the digital information signal in the area 1 is still in the validperiod, the magnetic tape 60 is fed fast forward. The recording date inthe area 2 is then referenced, and if it is within the valid period, therecord mode is provisionally cancelled and an input from the user isawaited. Even when the valid period for the software recorded stillremains unexpired, if the particular software is unrequired, the usersets the recording-reproducing system 300 to REC mode thereby to recordin the area 1 or 2. If the entire software is still needed, on the otherhand, the magnetic tape 60 is changed. This operation is performed inREC stand-by mode.

The area-divided configuration of the tape allows uniform access to thethree areas. The resulting effect is to disperse tape damage andlengthen the service life of the magnetic tape 60. Thus the user is notrequired to unload the magnetic tape 60 frequently from therecording-reproducing system 300 paying attention to the residual volumeof the magnetic tape 60, thereby improving the mechanical reliability.Also, since the record-start position is known in advance, the search iseffected at very high speed. Further, the recording-reproducing system300 can be controlled in simple manner for a lower hardware cost.

In the above-mentioned configuration, two areas are used for a digitalinformation signal exceeding two and half hours in recording time. Asshown in FIG. 20, the record information can be accommodated not in thetail portion of the area 3 but may be in the portion immediatelyfollowing the digital information recording section. In similar fashion,the record information for the areas 1 and 2 may be accommodated in theportion immediately following the digital information signal recordingsection of each area.

These recording time and recording date signals may be accommodated inthe ID section indicated in FIG. 4. Generally, however, the magnetictape 60 is often in stationary state at the end of viewing a software.The use of the format described in FIG. 20, therefore, quickens thesearch speed. Also, in the case where the user stops the magnetic tape60 in the middle of an area, the magnetic tape 60 is fed fast forward orrewound to the record information section of the particular area.

FIG. 21 shows a magnetic tape format according to another embodiment. Inthis embodiment, the recording information is recorded in accordancewith the format of FIG. 21 at the head of an area immediately beforestart of recording and at the head of the next area immediately afterthe end of recording. The feature of this format is that since therecording information for a different area is accommodated at the startof the areas 2 and 3, the search speed is further increased as comparedwith the embodiment shown in FIG. 20.

The area-divided system for the recording magnetic tape 60 is describedabove. In the recording-reproducing system 300 shown in FIGS. 1 and 19,however, the digital information signal may be recorded sequentiallyfrom the head of the magnetic tape 60 without dividing it into areas.

The area-recorded information is preferably recorded for about tenseconds and written in multiplex in consideration of a high-speedsearch.

In the system described above, the next REC stand-by signal may beinputted during reproduction of the digital information signal recordedby the recording-reproducing system 300. In such a case, the magnetictape 60 is immediately fed fast forward or rewound to the next area toready for recording. At the same time, provision is made to indicate theREC stand-by mode on the TV screen or in a part of the receiver. Then,in the case where the recording-reproducing system 300 enters the RECmode, the screen is switched to normal TV broadcast to indicate REC orturned off. This control operation can be easily performed normally bythe micro-computer mounted on the VTR.

A normal video signal processing circuit can of course be connected tothe recording-reproducing system 300 to permit the recording of the TVbroadcast as in the prior art.

It will thus be understood from the foregoing description that accordingto the present invention, there is realized a digital informationrecording-reproducing apparatus for transmitting the softwareinformation like audio or video through radio wave or cable andrecording/reproducing them, comprising the function of reducing therecording time to 1/n and expanding it to the original length on timebase at the time of reproduction. At the same time, the reliability ofthe reproduced data is improved and the decoder circuit and the trackingcontrol circuit are simplified. Further, the software informationrecorded is protected.

As described above, according to the invention, there is provided asystem for selling or renting the software like audio or video throughradio wave or cable, wherein the information on customers, rentalperiod, etc. can be easily managed.

Also, as explained above, by using the magnetic recording-reproducingapparatus according to the invention, the digital information signaltransmitted through a satellite or cable can be recorded accurately.

Further, according to another embodiment, the magnetic tape is dividedinto areas for recording, thus permitting high-speed search andlengthening the service life of the magnetic tape.

We claim:
 1. A digital information recording-reproducing apparatus forrecording a digital information signal temporally compressed to 1/n on amagnetic tape at a predetermined speed and reproducing the recordeddigital information signal at a speed 1/n times said predeterminedspeed, and for expanding the 1/n-compressed digital information signalby a factor of n, comprising:means for encoding said digital informationsignal compressed temporally to 1/n in a predetermined format; aplurality of magnetic heads mounted on a rotary drum for recording theencoded digital information signal and reproducing the recorded digitalinformation signal; means for rotating said rotary drum at apredetermined rotation speed and running said magnetic tape at apredetermined speed at a time of recording, and rotating said rotarydrum at a speed m/n (1<m≦n) times said predetermined rotation speed andrunning said magnetic tape at a speed 1/n times said predetermined speedat a time of reproduction; and means for decoding the reproduced digitalinformation signal in accordance with said predetermined format.
 2. Adigital information recording-reproducing apparatus comprisingdemodulation means for receiving and demodulating a digital informationsignal encoded in a first format, temporally compressed to 1/n,modulated and transmitted, recording-reproducing means for recordingsaid demodulated digital information signal on a magnetic tape at apredetermined rate and reproducing said recorded digital informationsignal at a rate 1/n times said predetermined rate, and, expanding said1/n-compressed digital information signal by a factor of n, and firstdecoding means for decoding said reproduced and expanded digitalinformation signal in accordance with the first format, wherein saidrecording-reproducing means comprises:second encoding means for encodingsaid demodulated digital information signal in accordance with a secondformat; a plurality of magnetic heads mounted on a rotary drum forrecording and reproducing the demodulated digital information signalencoded in said second format; means for rotating said rotary drum at apredetermined rotation speed and running said magnetic tape at apredetermined speed at a time of recording, and rotating said rotarydrum at a speed m/n (1<m≦n) times said predetermined rotation speed andrunning said magnetic tape at a speed 1/n times said predetermined speedat a time of reproduction; and second decoding means for decoding saidreproduced demodulated digital information signal in accordance withsaid second format.
 3. A digital information recording-reproducingapparatus according to claim 1, wherein the digital information signaltemporarily compressed to 1/n has additional information attachedthereto and is recorded on said magnetic tape at said predeterminedspeed, said encoding means includes means for generating a control codefrom the additional information attached to the digital informationsignal, the control code is recorded with the digital informationsignal, said decoding means includes means for detecting the controlcode from the reproduced digital information signal, and said decodingmeans decodes the reproduced digital information signal only when aresult of detection satisfies predetermined conditions.
 4. A digitalinformation recording-reproducing apparatus according to claim 3,wherein the control code includes information representing a type of thedigital information signal, and said decoding means decodes the digitalinformation signal only when the digital information signal is of aspecific type at the time of reproduction.
 5. A digital informationrecording-reproducing apparatus according to claim 3, wherein thecontrol code includes information representing a date of recording ofthe digital information signal, and said decoding means decodes thedigital information signal only when more than a predetermined periodhas not elapsed from the recording date at the time of reproduction. 6.A digital information recording-reproducing apparatus according to claim3, wherein the control code includes information representing a selectedone of a recording means and a recording person, and said decoding meansdecodes the digital information signal only when the selected one of therecording means and the recording person coincides with the selected oneof the recording means and the recording person respectively at the timeof reproduction.
 7. A digital information recording-reproducingapparatus according to claim 3, wherein the digital information signalis encrypted, the control code includes information for decrypting thedigital information signal, and the digital information signal isdecrypted using the control code at the time of reproduction.
 8. Adigital information recording-reproducing apparatus according to claim1, wherein a scanning pitch of said magnetic heads at the time ofreproduction is 1/m times a scanning pitch of said magnetic heads at thetime of recording.
 9. A digital information recording-reproducingapparatus according to claim 2, wherein a scanning pitch of saidmagnetic heads at the time of reproduction is 1/m times a scanning pitchof said magnetic heads at the time of recording.
 10. A digitalinformation recording-reproducing apparatus for recording a digitalinformation signal temporally compressed to 1/n on a magnetic tape at apredetermined speed and reproducing the recorded digital informationsignal at a speed 1/n times said predetermined speed, and for expandingthe 1/n-compressed digital information signal by a factor of n,comprising:means for encoding said digital information signal compressedtemporally to 1/n in a predetermined format; a plurality of magneticheads mounted on a rotary drum for recording the encoded digitalinformation signal and reproducing the recorded digital informationsignal; means for rotating said rotary drum at a predetermined rotationspeed and running said magnetic tape at a predetermined speed at a timeof recording, and rotating said rotary drum at said predeterminedrotation speed and running said magnetic tape at a speed 1/n times saidpredetermined speed at a time of reproduction; and means for decodingthe reproduced digital information signal in accordance with thepredetermined format; wherein a scanning pitch of said magnetic heads atthe time of reproduction is 1/n times a scanning pitch of said magneticheads at the time of recording.
 11. A digital informationrecording-reproducing apparatus comprising demodulation means forreceiving and demodulating a digital information signal encoded in afirst format, temporally compressed to 1/n, modulated and transmitted,recording-reproducing means for recording said demodulated digitalinformation signal on a magnetic tape at a predetermined rate andreproducing said recorded digital information signal at a rate 1/n timessaid predetermined rate, and, expanding said 1/n-compressed digitalinformation signal by a factor of n, and first decoding means fordecoding said reproduced and expanded digital information signal inaccordance with the first format, wherein the recording-reproducingmeans comprises:second encoding means for encoding said demodulateddigital information signal in accordance with a second format; aplurality of magnetic heads mounted on a rotary drum for recording andreproducing the demodulated digital information signal encoded in saidsecond format; means for rotating said rotary drum at a predeterminedrotation speed and running said magnetic tape at a predetermined speedat a time of recording, and rotating said rotary drum at saidpredetermined rotation speed and running said magnetic tape at a speed1/n times said predetermined speed at a time of reproduction; and seconddecoding means for decoding said reproduced demodulated digitalinformation signal in accordance with said second format; wherein ascanning pitch of said magnetic heads at the time of reproduction is 1/ntimes a scanning pitch of said magnetic heads at the time of recording.